1. Field of the Invention
This invention relates to an electromagnetic diaphragm pump, and particularly to an electromagnetic diaphragm pump which can easily be assembled and improve the pump efficiency.
2. Description of the Prior Art
A conventional electromagnetic diaphragm pump is described by using the drawings. FIG. 14 is a cross-sectional view of the conventional electromagnetic diaphragm pump, FIG. 15 is a plan view of the diaphragm pump of FIG. 14, and FIG. 16 is a side view along the X--X line of FIG. 15.
In these figures, a housing 1 is made by the press operation of a metal plate, and each of side plates 1A is punched with a circular hole 1B, the side plates being bent at both ends thereof so as to oppose each other.
A pair of diaphragm plates 2 are fitted into the circular holes 1B, respectively. The expanded peripheral portion of each diaphragm 4 made of an elastic material such as rubber is pinched by and between corresponding the diaphragm plate 2 and a head cover 3. Each symbol 100D represents the fitting portion or recess which is formed in the diaphragm plate 2 and receives the expanded peripheral portions of the diaphragms 4. The diaphragm plate 2, the head cover 3 and diaphragm 4 are attached to the side plate 1A of the housing 1 using screws 18.
A pair of plate-like magnets 8 are held in a plate-like magnet holder 6 which is a part of an electromagnetic diaphragm pump and preferably formed of a material such as aluminium. The pair of diaphragms 4 are attached to both ends of the magnet holder 6 by using pressing tools 5 and screws 7. The magnet holder 6 and magnets 8 constitute a vibrator of the electromagnetic diaphragm pump.
Inside each head cover 3, a diaphragm chamber 3A is formed. On each diaphragm chamber 3A, there are formed an intake port 14A and a discharge port 15A, which are provided with an intake valve 14 and a discharge valve 15, respectively.
Each field core 9 is an iron core of laminated silicon steel pates in the shape of "E", and, as shown in FIG. 15, the central leg thereof is fitted in a coil 11 wound around a bobbin 10.
The electromagnetic diaphragm pump is provided with two such field cores 9, which are fixed to the bottom of the housing 1 using bolts 12 and nuts 13 so as to sandwich the magnet holder 6. Since it is needed to support the field cores 9 apart from the bottom of the housing 1 by a predetermined distance, a sleeve 16 is passed through with the bolt 12 as shown in FIG. 16.
Such electromagnetic diaphragm pump is attached through, for instance, rubber vibration insulators 19, to a fluid tank 20 as seen in FIG. 14. A pressurized fluid such as air is discharged into the tank 20 as shown by an arrow C via a tube 17 connected to the head cover 3.
FIG. 17 is a schematic plan view for showing the operation principle of the electromagnetic diaphragm pump. In FIG. 17, the symbols same as those in FIG. 14 or FIG. 16 indicate the same or identical portions.
A pair of magnets 8 attached to the magnet holder 6 are arranged, as shown, so that the magnetic poles of the pair of magnets 8 are reverse to each other. Accordingly, if the coil is supplied with an a.c. current so that a magnetic flux passes from one field core 9 to the other field core 9 in the direction of a solid arrow P or a dotted arrow Q, the magnet holder 6 is reciprocated in the direction of an arrow R by the attractive and repulsive actions between the magnets 8 and a magnetic flux P or Q, whereby the diaphragm 4 is vibrated.
As a result, as shown in FIG. 15 by an arrow A, a fluid is sucked into the diaphragm chamber 3A through the side plate 1A of the housing 1, an opening 1D formed in the diaphragm plate 2 and head cover 3, the intake port 14A and intake valve 14, and the fluid passes through the discharge port 15A and discharge valve 15 as shown by the arrow B and then the fluid is dis-charged from the tube 17 into the fluid tank 20 as shown by the arrow C in FIG. 14.
Such electromagnetic diaphragm pump is described in, for instance, the Japanese Patent Laid-open Publication No. Showa 61-252881 and the Utility Model Laid-open Publication Nos. Showa 63-100682, 63-112285 and 61-137892.
The above described prior art had the following problems.
(1) As previously described, the field cores 9 are attached to the housing using bolts 12 and nuts 13. Here, the holes for insertion of the bolts 12 formed in the bottom of the housing 1 and the field cores 9 have a diameter that is little larger than the outer diameter of the bolts. Accordingly, a jig is required to accurately position and attach the field cores 9 to the housing, so the attaching work is cumbersome. PA1 (2) The housing is made by a press work of a metal plate, and as a result, the dimensional accuracy of the various portions of the housing is difficult to increase. For instance, it is very difficult to accurately establish the distance between the pair of side plates 1A in each of which the attaching hole or the circular hole 1B is formed for fitting the diaphragm plate 2 of the diaphragms 4.
Also, even if the positioning was performed accurately enough, after the assembling of the electromagnetic diaphragm pump, the attaching positions of the field cores 9 can shift when the pump is transported, or when it is operated. If the attaching position of the field cores 9 shifts, the field cores 9 may move away from the vibrator to decrease the efficiency of the electromagnetic diaphragm pump, or the field cores 9 may move toward the vibrator to lose the balance of the vibration and reduce the durability of the diaphragms.
Therefore, it is difficult to accurately set the distance between the pair of diaphragms 4, which in turn will make it difficult to improve the efficiency of the electromagnetic diaphragm pump to the greatest extent.